Furnace



E. G. BAILEY FURNACE 2 Shets-Sheet 1 Filed Nov. 6, 1951 LINVENTORErr/[g1 fial'ley FURNACE Filed Nov. 6, 1931 2 Sheets-Sheet 2 INVENTORErvin Bailgy /Y HIS AMTORN Y Patented Aug. 27, 1935 UNITED STATESFURNACE Ervin G. Bailey, Eaaton, Pa", assignor to Fuller Lehigh Company,New York, N. Y., a corporation of Delaware Application November 6, 1931,Serial No. 573,344

2 Claims.

- My invention relates to a furnace, and particularly a. furnace whereinfuel in finely divided form is projected toward a pool of moltenmaterial.

' The invention is especially useful in connection I with furnaces inwhich pulverized coal is used as a fuel, and in which ash in thepulverized coal is deposited in molten form in the bottom thereof.

One object of the invention is the provision of a furnace wherein a poolof molten material radiates its heat upwardly and assists in theignition and combustion of an entering fuel stream. Another object isthe construction of such a furnace in a. manner which will permitreversal of direction by the stream of burning fuel in contact with thepool, to the end that particles of molten, incombustible material may beseparated from the burning stream by inertia and change of direction,and by contacting with the sticky surface of the pool. A further objectis the collection of unburned carbon particles upon the surface of thepool where they may float and subsequently burn. Still a furtherobjectis to create a high temperature in the pool by direct impingementof the flame thereon. Other objects will be apmrent upon considerationof the present specification.

The invention is shown by way of illustration in. the accompanyingdrawings in which- Figure l is a vertical mid-section of a furnaceconstructed in accordance with the invention, and

Fig. 2 is a vertical mid-section of another furnece constructed inaccordance with the invention:

In the combustion of fluid fuel, particularly pulverized coal, it isdesirable to complete the buming of the fuel in the combustion chamber;that is to say, before the hot gases come in contact with the objectwhich it is desired to heat; for instance, the tubes of a boiler. I havediscovered that the radiant surface of a pool of molten material-forexample, slag-in the bottom of the combustion chamber may be utilized togive added heat to the stream of fuel entering the furnace and thusaccelerate combustion and increase the rate of heat release from thefuel. Combustion of the fuel may thus be completed in the furnaceproper, and the size of the furnace may thus be considerably restricted.I have also found that the surface of the molten pool may be employedfor giving a secondary mixing to the entering fuel stream and air andfor separating incombustible material from the fuel stream.

In the accompanying drawings there is shown a furnace including acombustion chamber ill, a

boiler l l, and a. boiler setting l2 above the combustion chamber. Amolten pool i3 is shown in the bottom of the combustion chamber ID, andpositioned above this pool is a burner M which is adapted to project anignited jet of slag-bearing fuel 15 approximately vertically toward thepool and into contact therewith. The burner I4 is preferably a fuel andair mixer, and may be constructed in any known or desirable form. I mayemploy, for example, a. burner similar to that described and illustratedin my copending application for Fuel burner filed September 27, 1930,Serial No. 484,739. The burner is positioned in the roof it of thefurnace above part of the pool l3, and the mixed fuel and. air issuingtherefrom is projected substantially vertically, changes its directionof travel in contact with the pool, and passes upward into a gas passagei! above a part of the pool wherein the boiler and water tubes i8forming a part of the boiler are disposed. The outlines of the fuelstream and resulting combustion gases are indicated very generally bybroken lines extending from the burner l4.

As the jet of burning fuel comes in contact with the molten pool andreverses its direction, particles of slag from the fuel together withother unburned or incombustible material are thrown outwardly and intothe pool by centrifugal force and gravity. Unbumed particles of carboncoming upon the surface of the pool will float there and, absorbing heatfrom the pool while being swept by air from the burner, will burn andadd heat to the combustion chamber. The resulting combustion gasespartially freed from both the incombustible solids and ash, now inliquid form, pass upward among the boiler tubes with less ash thanotherwise.

Materiel other than ash or slag may be added to the molten pool.Examples of such material are fly ash, dust, or if necessary, somefluxing material.

It will be apparent that, by using the radiant heat of the pool ofmolten slag or other material, as indicated, a maximum temperature isgiven the entering stream of fuel and air, causing early ignition andintense combustion. Contact of the fuel stream with the surface of themolten pool affords secondary mixing of the fuel and air, that is tosay, a mixing similar to that which occurs at the turbulent burner. Asmaller furnace than would otherwise be required is thereby madepossibie.

As has been indicated above, the flame impinges upon the slag poolbefore turning upwardly and passing to the boiler tubes, The pool thusplays a part in the reversal of the flame direction. The combineddistance of the burner from the slag pool and the distance from the slagpool to the boiler tubes is such that the flame temperature has time toreach a sufficiently high point to melt the ash and to burn away orgasify the combustible material in the fuel. At normal feedsubstantially all of the ash is melted before the flame contacts withthe poolfittnd the upstream from the pool to the boiler is a gaseousflame.

The functions of the pool, therefore, are to re fiect and radiate heattoward the burner, and the incoming mass of air and burning fuel, and

cause more rapid and complete ignition of the fuel stream entering thefurnace, to shorten the flame, to aid in the reversal of the flame, toaid in mixing the air and fuel, thus acting as a secondary mixture afterthe primary mixing which occurs in the burner, and to separate from thefuel stream incombustible materials which are brought in contact withthe sticky surfaces of the pool as the fuel stream reverses itsdirection.

Since the slag pool l3 extends horizontally beyond the roof it andbeneath the water tubes is, it will be obvious that the slag pool alsoacts to promote heat absorption, by radiation to the boiler tubes. Heatabsorption by the boiler tends to freeze the slag pool, while the flameprojected by the burner tends to keep it molten. Projection of the flamedownwardly into contact with the pool insures its molten state for lowerboiler rating than other forms of firing. In the constructionillustrated in Figure 2, a somewhat difierent type of furnace isillustrated. This construction shows the application of the invention toa furnace in which the distance from the roof through which the fuel isprojected to the furnace floor is somewhat greater than that in thefurnace illustrated in Figure 1. Furthermore, Figure 2 shows a furnacewherein the roof it has a greater slope than the roof it in Figure 1.The fuel jet I5 in this construction is also illustrated as having aslight angle to the verticalas contrasted with the direction of the fueljet E5 in Figure l which is approximately vertical.

From the above, it will be apparent that in each of the modificationsdisclosed, a relatively high heat release per cubic foot of furnacevolume, per unit of time, is made possible. The vertical distance from.the slag pool to the burner tip is suflicient to permit substantialcoking of the fuel particles, yet is short enough for the fuel stream toimpinge against the slag pool and to provide the advantageous secondarymixing of the fuel stream which aids in accelerating combustion so thatit may be completed within a relatively small distance of flame travel.The slag pool provides an effective target for the fuel stream and aidsin the provision of a higher furnace temperature and an early ignitionof the incoming fuel. The fuel and air mixing type of burner aids alsoin the acceleration of the combustion process. It will be observed thatin each modification the aoiacis has been particularly described as aboiler fur-- nace, it will be recognized that the invention is equallyapplicable to other fuels in fluid or finely comminuted form, and tofurnaces other than boiler furnaces. Furthermore, the description heregiven and the furnaces illustrated in the drawings are merely presentedas examples of how the invention may be applied. Other forms of theinvention will readily suggest themselves to those dealing withcombustion problems, which do not depart from the invention or theproper scope of the appended claims.

With this understanding, therefore, I claim:

1. In the method of operating a downwardly fired pulverized fuelfurnace, the steps consisting of maintaining over the floor of saidfurnace a molten slag pool having a horizontal dimension greater thanthe vertical distance from said slag pool to ariginlet for pulverizedfuel and air, mixing a stream of pulverized fuel with sumcient air tocause complete combustion thereof, igniting and driving said streamdownwardly toward the slag pool for a distance sufiicient to causesubstantially complete coking of the fuel particles prior to contact ofthe stream with the pool, deforming the stream by impact with the moltenpool, and spreading the stream along the aforesaid horizontal dimensionover the molten slag pool for a distance greater than the verticaldistance between the stream entrance and the slag pool; and thencedirecting the burning fuel stream upwardly through an outlet.

2. In a slag-tap furnace, the combination of upwardly-extending sidewalls defining a combustion chamber having a gas outlet in the upperportion thereof; a furnace bottom extending across the lower end of thechamber and constructed to sustain a pool of slag thereon; and burnermeans spaced from the gas outlet and at one side of the furnace forintroducing downwardly toward the adjacent side of the slag pool aturbulently-mixing stream of pulverized fuel with suificient air forsupporting combustion thereof; the burner means being spaced from theslag pool a distance sufiicient to effect substantial coking of the fuelin suspension, yet close enough to cause the stream to impinge againstthe slag pool; the slag pool having a horizontal dimension greater thanthe distance between the slag pool and the burner means so as to eflecta thorough secondary mixing of the fuel and air and to provide amplespace for the stream to turn upward toward the outlet.

ERVIN G. BAILEY.

